Tsunamis generated by earthquakes generally propagate as long waves in the deep ocean and may be mathematically described by the shallow water equations (SWEs). Tsunami propagation and inundation usually involve a vast problem domain, which requires a highly efficient numerical model to provide accurate predictions. In this work, a hydrodynamic model that solves the 2D SWEs using a finite volume Godunov-type shock-capturing scheme is comprehensively tested on different hardware devices, covering both Central Processing Units (CPU) and Graphics Processing Units (GPU), for efficient tsunami modeling.
Tsunamis may cause huge loss of lives and economic damage as evidenced by the 2004 Indian Ocean event and the 2011 Japan event. Numerical prediction of the tsunami propagation and inundation provides essential information for evacuation management, risk assessment, city planning and structural design. Numerical models are also an indispensable component in most of the tsunami forecasting and warning systems.
Tsunami propagation and inundation can be mathematically represented by the shallow water equations (SWEs) or Boussinesq equations with an acceptable level of accuracy. Most of the prevailing tsunami models solve the SWEs or Boussinesq equations using finite difference methods (FDM) (Imamura, 1996; Titov and Synolakis, 1995), finite volume methods (FVM) (Leveque et al., 2011), finite element methods (FEM) (Tinti et al., 1996) or smoothed particle hydrodynamics (SPH) (Benedict and Robert, 2008). However, a tsunami event usually takes place in a vast domain and assessment of tsunami impacts may need multi-scale simulations that can accurately predict wave propagation across the ocean as well as inundation in urban areas requiring high-resolution representation of the topographic features. The high computational demand of this type of modeling exercises hinders wider application of most of the existing tsunami models.
In order to improve the computational efficiency of tsunami models to facilitate multi-scale simulations, different approaches have been widely reported in literature, including adaptive mesh refinement (e.g. Leveque, et al., 2011; Popinet, 2011) and parallel computing (e.g. Lavrentiev-jr et al., 2009; Pophet et al., 2011). In recent years, attempts have also been made to explore the potential of the graphics processing units (GPU) for improving model performance. GPU accelerated models have been presented in computational biophysics (Owens et al., 2008), computational fluid dynamics (Crespo et al., 2011), computational hydraulics (Brodtkorb et al., 2012; Smith and Liang, 2013), among other fields. More recently, authors have also attempted to develop CUDA-based GPU models (Vazhenin et al., 2013; Amouzgar et al., 2014) for tsunami simulations to further demonstrate the potential of this modern high-performance computing technology. However, the model performance across different devices has not yet been adequately compared to fully justify the benefit of this new development.
Xiong, Yan (Hohai University) | Liang, Qiuhua (Hohai University) | Amouzgar, Reza (Newcastle University) | Cox, Daniel T. (Newcastle University) | Mori, Nobuhito (Oregon State University) | Wang, Gang (Kyoto University) | Zheng, Jinhai (Hohai University)
This paper concerns tsunami modeling from wave propagation to inundation of dense urban area through reproduction of a laboratoryscale event. The adopted hydrodynamic model is based on the finite volume shock-capturing solution to the 2D nonlinear shallow water equations and is implemented on modern graphics processing units (GPUs) to achieve high-performance simulations. After being validated through reproduction of flow hydrodynamics, the model is further applied to quantify the tsunami impact on urban building structures by calculating pressure forces.
Tsunami represents a major type of natural hazards to the world’s coastlines. Once it happens, a tsunami may cause wide-spreading damage to both natural and social systems, and kill lots of lives. For example, the 2004 Boxing Day Tsunami, triggered by the M9.3 undersea earthquake offshore Sumatra, inundated a large number of coastal communities with waves up to 30m along the Indian Ocean coastline and killed 230,000 people in 14 countries. It was recorded as one of the deadliest natural disasters on book. On 11th March 2011, 20min after the M9.0 Tohoku earthquake, a mega tsunami struck East Japan coastline, travelled up to 10km inland with a maximum runup of over 40m, caused over 15,000 deaths and wide-spreading damage to buildings and infrastructure, including nuclear power stations. Tsunamis have long been perceived as extremely rare events. But worldwide statistics shows that, on average, one damaging tsunami event per year has been reported in the past two decades and tsunami is actually a common type of natural hazards of medium probability and potentially high risk to the world’s coastlines (NOAA Center for Tsunami Research 2016).
In order to protect coastal communities and save lives, attention has been given to better plan and design buildings and structures along the coastlines that are under threat of tsunamis, generally by following building guidelines/codes provided by relevant institutions in different countries, e.g. the Building Center of Japan’s Structural Design Method of Buildings for Tsunami Resistance (SMBTR) (Okada et al., 2004), Federal Emergency Management Agency (FEMA)’s Coastal Construction Manual (FEMA, 2011). Particularly, the Guidelines for Design of Structures for Vertical Evacuation (FEMA, 2012) suggests that the impact of tsunami forces may classify onto hydrostatic force, buoyant force, hydrodynamic force, impulsive force, debris impact force, debris damming force, uplift force and additional gravity load from the retained water on elevated floors.
Chen, Kaicui (Hohai University) | Liang, Qiuhua (Hohai University) | Xiong, Yan (Newcastle University) | Qiang, Juan (Hohai University) | Wang, Gang (Hohai University) | Zheng, Jinhai (Hohai University)
Storm surge and tsunami may induce extreme flow/wave conditions and cause tremendous damage to human lives, buildings and structures in the coastal areas. Bridges are among the most vulnerable structures to these extreme hazardous flows/waves. With a focus on sea-crossing bridges where the piers may be the only/main structure receiving flow/wave impact, this work presents a series of laboratory experiments to investigate the extreme flow/wave impact on a simplified bridge model. Subsequently, the experimental measurements are used to validate a hydrodynamic model for reliable prediction, with results further compared with those estimated using standard design formulae.
Storm surges and tsunamis may drive destructive flows and massive volumes of water onshore and cause tremendous damage to the coastal areas (Saatcioglu et al., 2005; Robertson et al., 2007). In addition to their direct threat to human lives, the resulting extreme waves and flooding may cause damages to and even destroy buildings and other structures. For example, in 2005, the extreme storm surge and floods following Hurricane Katrina caused the failure of man-made levees, rapidly inundated majority part of New Orleans, killed more than 1,833 people and left over one million people homeless (Robertson et al., 2007). On 11th March 2011, a mega tsunami struck East coast of Japan, travelled up to 10 km inland with a maximum run-up of over 40m, leading to over 15,000 deaths and wide-spreading damage to buildings and infrastructure, including nuclear power stations (Maruyama et al., 2012).
Field missions have been conducted following major tsunami and storm surge events to survey the wave and flood damages to buildings and infrastructure, trying to gain better understanding of extreme wave/flow-structure interaction and learn lessons (Iemura et al., 2005; Ghobarah et al., 2006; Akiyama et al., 2012). Particularly, a large number of bridges in coastal areas have been reported to be damaged and collapse during these extreme events. There are typically three types of failure mechanisms, i.e. 1) bridge superstructure (decks) failure, 2) bridge superstructure-substructure connection failure, and 3) bridge substructure (abutments, supporting piers and foundations) failure. Due to the relatively low deck height of the coastal and traditional bridges, they may be overtopped and submerged during the extreme disastrous events, most commonly leading to superstructure failures and connection failures. These failure modes have been often observed after tsunamis or extreme storm surges. For this reason, most of the current studies related to extreme wave/flow impact on bridges have been focused on vertical and horizontal loading on superstructures (Chen et al., 2009; Bradner et al., 2010; Azadbakht and Yim, 2014; Seiffert et al., 2014a; Hayatdavoodi et al., 2014b).
Storm surge is a major cause of coastal flooding. Robust models have provided useful tools for storm surge forecasting and flood risk management. In this work, a finite volume shock-capturing shallow water equation model originally developed for flood simulation is improved and tested for storm surge modeling. For storm surge modeling, additional source terms are included to represent the wind stresses and atmospheric pressure variation. The performance of the improved model is validated and demonstrated through application to benchmark test cases.
Storm surges and the resulting coastal floods caused by hurricanes, cyclones and typhoons are a major type of natural hazards threatening many coastal cities worldwide. Nowadays, numerical modeling has provided an indispensible tool for forecasting storm surge and managing the resulting flood risk. Numerous models that can be used to simulate storm surge and the resulting flooding processes have been reported in literature in the last few decades. Most of these models are based on the solutions to the governing depth-average fluid equations using finite element, finite difference or finite volume numerical schemes.
Ip et al. (1998) presented a finite element Galerkin model for simulating tidal flooding and drying in shallow estuaries with applications to hypothetical embayment and to the Great Bay, New Hampshire estuary system. The ADvanced CIRCulation (ADCIRC) is a two-dimensional, depth-integrated, barotropic time-dependent long wave, hydrodynamic circulation model based on an unstructured finite element numerical scheme (Leuttich et al., 1992; Blain et al., 1994); it has been widely used for predicting coastal circulations and storm surges. However, due to the adoption of unstructured grids, the ADCIRC model is computationally too demanding to provide high-resolution ensemble forecasts in an efficient way. Westerink et al. (1992) reported another unstructured grid-based finite element model to calculate tides and hurricane driven storm surges in the Gulf of Mexico, in a region ranging from the South Mississippi to the northwest coast of Florida.
Tsunamis generated by earthquakes generally propagate as long waves in the deep ocean and develop into sharp-fronted surges moving rapidly towards the coast in shallow water, which may be effectively simulated by hydrodynamic models solving the nonlinear shallow water equations (SWEs). However, most of the existing tsunami models suffer from long simulation time for large-scale high-resolution real-world applications. In this work, a graphics processing unit (GPU) accelerated finite volume shock-capturing hydrodynamic model is presented for efficient tsunami simulations. The model is demonstrated to consistently save approximately 40 times of computational cost for all of the benchmark tests.
Artificial reefs have been utilized throughout the world for many different purposes. The majority of artificial reefs globally are related to fisheries ecology and management. In fact, artificial reefs are capable of attracting and aggregating fishes as well as enhancing the habitats of other marine organisms in its vicinity. In order to design an artificial reef that is fit for purpose, maintains its structural integrity and is environmentally friendly, it is necessary to have a good knowledge of the hydrodynamics in its vicinity. This paper proposes a procedure for obtaining this information in the early design stage with a minimal amount of intervention offshore. A fully 3D model has been applied to investigate the hydrodynamics around a reef such as the wake region effect on the reef ecology.
This work aims to design physical experiments and test a numerical model for investigating surge-like wave impact on urban structures. Flume experiments are being conducted to evaluate the benefit of an embankment-like structure constructed in front of the buildings for hydrodynamic impact reduction. A finite volume Godunov-type hydrodynamic model is improved and tested for calculating surge induced pressures on structures. Validation against an independent laboratory test demonstrates that the model can be applied to reproduce the current laboratory tests and may be used for more general purposes of evaluating surge impact and facilitating practical design.
Al-Bourae, Yassir (School of Marine Science and Technology, Newcastle University) | Downie, Martin (School of Marine Science and Technology, Newcastle University) | Liang, Qiuhua (School of Civil Engineering and Geosciences, Newcastle University)
This paper introduces a coastal modeling tool based on the solution of the 2D shallow water equations on a novel adaptive Cartesian grid system. While providing dynamically adaptive solutions, the new grid system is easy to implement, and it maintains the desirable property of a structured Cartesian grid. On such a grid, the governing equations are solved using a finite volume Godunov-type scheme that is designed to ensure non-negativity of water depth for applications involving a moving shoreline over complex domain topography. The new model is validated against several analytical and numerical benchmark tests.
It is estimated that more than 38% of the world’s population lives within 100 km and 44% within 150 km of a coast. Coastal zones are thus economically and politically important for most countries or regions. Hence, it is vitally important to understand the different coastal processes driven by waves and currents, and to protect or reform our coastlines. At the heart of this is to accurately model the coastal hydrodynamics that provides the driving force for other processes. This has long been an active research topic; numerous computer models have been developed and reported, and Brocchini and Dodd (2008) gave a useful review. Models based on the solution to the depth-averaged shallow water equations (SWE) represent a wide range of applications (e.g., Dodd, 1998; Hu et al., 2000; Hubbard and Dodd, 2002). A coastal zone may cover a large area and is normally featured by complicated topographies and geometries, where very complex local hydrodynamic phenomena can develop. Thus a model should possess certain features in order to give reliable solutions to a related problem. Basically a successful shallow flow model for coastal simulation should be able to represent complex domain topographies and geometries, handle a moving shoreline and perform efficient simulation for large-scale problems.
Wu, Xingzheng (School of Civil Engineering and Geosciences, Newcastle University) | Hall, Jim (School of Civil Engineering and Geosciences, Newcastle University) | Liang, Qiuhua (School of Civil Engineering and Geosciences, Newcastle University)